Recently, plant-derived resins have been drawing attention as a replacement for petroleum raw materials, and practical applications of resin compositions utilizing various plant-derived resins are being actively investigated. One example of a resin composition utilizing a plant-derived resin that has recently been drawing particular attention is biodegradable resins such as polylactide, which are now being commercialized in various applications. The applications of biodegradable resins are extremely diverse, ranging from applications having a short usage period which presuppose being discarded, such as containers and packaging or films used in agriculture, to highly functional applications capable of maintaining initial characteristics over a long period of time, such as the housing of home electric appliances, office-automation equipment or parts used in automobiles.
Most plant-derived resins are crystalline resins, which means that it is important to crystallize the resin in order for it to express its inherent material characteristics such as heat resistance and the like. The crystallization rate for many plant-derived resins is slow, so to obtain a molding in which crystallization has finished, it is necessary to either hold the resin for a long time during the mold processing in a mold adjusted to the crystallization temperature of the resin, or to subject the molded article to an annealing treatment at the crystallization temperature after molding. However, holding the resin for a long time during the mold processing in a mold is not only impractical, the resultant molding also tends to be insufficiently crystallized. Further, crystallization by annealing after molding has the drawback that the molded article tends to change shape during the crystallization process.
Accordingly, various methods have been proposed to improve the crystallization rate of plant-derived resins to solve the above-described problems. For example, Patent Document 1 (Japanese Patent Laid-Open No. 9-278991) describes that a molding, which has both transparency and crystallinity, can be obtained by adding a transparent nucleating agent such as an aliphatic acid amide to an aliphatic polyester such as polylactide.
Patent Document 1: Japanese Patent Laid-Open No. 9-278991